A standard motor-vehicle sliding door moves on tracks between a closed position and an open position. It is now standard to provide a drive for power-assisted and even remote operation of this door, which under the best of circumstances can be difficult to manipulate. Thus in a standard arrangement a pair of cable sections, which may be separate or parts of a common cable, each have one end anchored on the door and an opposite end anchored on a drum or respective coaxial sections of a drum. A drive gear rotated by a reversible electrical motor rotates the drum, depending on whether the door is to be opened or closed, paying out one of the cables and winding up the other cable.
In a standard arrangement as described in U.S. Pat. No. 5,046,283 of Compeau the drive motor and drum are mounted inside the vehicle and the cables are deflected about a fairly complex path from their attachment point on the door outside the vehicle to the interior drive unit. Such an arrangement is rather complex and, due to the numerous deflecting rollers over which the cables must pass, prone to failure at several high-stress locations. In addition installing the door, threading the cable into position, and generally getting the slider working is a substantial amount of work during the manufacturing process.
Another problem with these systems is that if the drive fails the door can be almost impossible to open. German utility model 296 13 848 describes an emergency-override system for a sunroof that requires a special tool that is inserted into the drive mechanism in order to operate it manually and/or override the motor drive. Such a system is extremely inconvenient and is basically only intended for use by equipped service personnel; it is not suitable for the end user to use in the field for an emergency exit from the vehicle.